[Asterisk-Users] Comparision of IAX2, FWD, iaxtel etc etc.

[Brian Capouch]

Wilson Pickett wrote:
>>The box inside talks first through the NAT gateway, and then the other
>>side finds its way back inside automagically.
> 
> 
> How would the IAX (host=dynamic) client first register? Am I missing something?

Firewalls generally don't block any usermode connections OUTBOUND from 
the hosts inside--that's why URLs can point to oddball ports, e.g. 8080, 
without any problem when one is, say, surfing the net.

That same technique allows the host at the far end of an IAX 
registration to establish the NAT binding, and thus know the correct 
port destination for the return traffic.

Since the connection is opened from the INSIDE, the NAT router doesn't 
block the return traffic.

Voila, as they say.  Since there isn't a separate media stream to NAT, 
the audio comes right in.

B.